1. Field of the Invention
The present invention relates, to an electronic flash device, although not limited to such a device for use with a photographic camera or for use in a photographic enlarger, and more particularly, relates to such an electronic flash device which is capable of single firing and successive multiple firings of one or more flash tubes.
2. Description of the Prior Art
When used with a photographic camera, the electronic flash device is required to emit a flash light not only a single time in each single-shot picture taking operation but also sequentially or successively in synchronization with successive photography for continuous shooting with a motor driven camera. The electronic flash may also be required to emit flash light successively for the purpose of illuminating an object to be photographed such that focusing of the camera objective lens can be adjusted automatically or manually with the aid of the flash light illumination or that the camera user can observed the lighting condition. It is further desirable if the electronic flash can also be used as a stroboscope for illuminating an moving object to be photographed so that successive stages of the movement can be recorded on a single picture frame. When the electronic flash device is used in a photographic enlarger as its light source, it is desirable that the electronic flash device emits a large amount of light at successive intervals for the exposure as well as a small amount of light successively at such a high frequency as to be regarded as continuously emitted, for the purpose of focusing, trimming and adjustment of enlarging multiplication.
U.S. Pat. No. 4,275,335 assigned to the same assignee as that of the present invention, discloses an electronic flash device which can emit a large amount of flash light for a single-shot picture taking as well as emit a small intensity of flash light continuously prior to an actual photography. However, the prior art device can not emit flash light successively at intervals.
U.S. Pat. No. 4,210,849 assigned to the same assignee, discloses an electronic flash device wherein the amount of light emitted therefrom can be limited so that the main capacitor of the device can be recharged to a desired level during the interval of successive photography for continuous shooting with a motor-driven camera. However, the device can not emit flash light successively at high frequency, because it takes considerable time for resetting the flash firing circuit.
Japanese laid-open patent application with laid-open No. Sho 50-134,636 shows an electronic flash device with a pair of flash tubes which are alternatively fired at a high frequency. However, the device can not make a single firing.